// Begin Theological lesson about Marriage
Although people in the old testament had multiple wives, there's a pretty specific new testament passage about marriage in 1 corinthians 7:
1 Now for the matters you wrote about: “It is good for a man not to have sexual relations with a woman.” 2 But since sexual immorality is occurring, each man should have sexual relations with his own wife, and each woman with her own husband. 3 The husband should fulfill his marital duty to his wife, and likewise the wife to her husband. 4 The wife does not have authority over her own body but yields it to her husband. In the same way, the husband does not have authority over his own body but yields it to his wife. 5 Do not deprive each other except perhaps by mutual consent and for a time, so that you may devote yourselves to prayer. Then come together again so that Satan will not tempt you because of your lack of self-control. 6 I say this as a concession, not as a command. 7 I wish that all of you were as I am. But each of you has your own gift from God; one has this gift, another has that.
Although not explicitly condemning polygamy, the implications are everywhere.
I'm sure there's other biblical passages condemning the practice, but the above one was the first that came to mind.
//End Theological Lesson on Marriage
So firstly, America was not founded on biblical values, but rather the idea of freedom. For a lot of the founding fathers who were actually deists, such as thomas jefferson, alexander hamilton, and thomas paine, this actually meant freedom from the "tyrannical" church of england...
Secondly, Polygamy is illegal in all 50 states, and the punishment for being married to more than one person ranges from Misdemeanor to Felony. See this map:
https://en.wikipedia.org/wiki/File:Polygamy_laws_usa.png
Edited 4/12/2016 19:38:42